A smashed window on the 24th floor of Yorkville Tower off 92nd Street marks the spot where Theri Sunnuz jumped to her death onto sports-club roof Sunday as her family came to visit. Photo: G.N. Miller

A woman plunged 21 stories to her death Sunday from a luxury Upper East Side condo tower in an apparent suicide, just hours before her family was about to pay her a visit, authorities and witnesses said.

Theri Sunnuz, 32, apparently used an object, possibly a chair, to smash a window on the 24th floor of the Yorkville Tower on Third Avenue near 92nd Street at around 12:15 p.m., authorities said.